Field of the Invention
The present invention relates to a control apparatus for an automatic transmission.
Description of the Related Art
An automatic transmission generally includes planetary gear mechanisms and engaging mechanisms such as a clutch and a brake, and implements each gear range by switching the power transmission path by the engaging mechanisms. As the engaging mechanisms, employing a mechanical engaging mechanism has been proposed in addition to a hydraulic engaging mechanism. In particular, an arrangement that uses a clutch (two-way clutch) capable of switching to a state to do two-way rotation restriction as a brake has been proposed (for example, Japanese Patent Laid-Open No. 2014-202340).
When the two-way clutch is used as a brake, a rotational element connected to the two-way clutch can be switched between a state in which rotation is restricted only in one direction (rotation in the reverse direction is permitted) and a state in which rotation is restricted in both directions. When switched to the state in which rotation is restricted in both directions, the rotational element connected to the two-way clutch is fixed to the casing. For this reason, if switching is done during rotation of the rotational element, unusual noise or vibration occurs, and the two-way clutch breaks. To prevent this, switching is performed after confirming that the rotational element stands still.
In an arrangement that switches the two-way clutch to the state to restrict rotation in both directions when switching the gear range to the reverse range, switching the state of the two-way clutch is needed before the reverse range is put in gear. To implement a smooth start, this operation is preferably quickly performed.